definitely you can
You can customize the view to add another
color column, or modify the formula in the template. The UI in the
template which takes in the sender information, creates a formula based
on what you specify, and saves it off as the column formula. At runtime,
we evaluate the formula which gives us back the RGB values of the background/font
text. So this formula can also contain the Subject or any other field
as you like. Please look at the mail template in the designer.